1. Field of the Invention
The present invention relates to a bearing assembly and a method of manufacturing the same, the bearing assembly being used in rotating portions of a computer and its peripheral devices.
2. Description of the Prior Art
As for a conventional bearing assembly constructed of a pair of ball bearing units A, B mounted on a rotary shaft D of rotating portions of a computer or its peripheral devices, as is clear from FIG. 2(a), it is necessary to produce its components separately. Consequently, a sleeve-like spacer C and such pair of the ball bearing units A, B are produced separately from each other. These components A, B, C of the conventional bearing assembly are then delivered to a user. After receipt of the components, the user mounts the components A, B, C on the rotary shaft D to complete the conventional bearing assembly, as shown in FIG. 2(b).
As described above, in the conventional bearing assembly, it is necessary for the user to mount the pair of the ball bearing units A, B and the spacer C on the rotary shaft D in a condition in which the ball bearing units A, B are spaced apart from each other through the spacer C. Consequently, the conventional bearing assembly suffers from the following problems:
(a) While keeping a sufficient rigidity, the rotary shaft D is required to be sized in outer diameter so as to engage with the inner race rings of the ball bearing units A, B; PA1 (b) Since the spacer C is a separate component independent of the pair of the ball bearing units A and B, it is necessary for the spacer C to have its opposite end surfaces improved in parallelism therebetween and also in flatness thereof, taken in connection with the dimensions of the ball bearing units A, B being assembled together with the spacer C; and PA1 (c) Since the spacer C is merely sandwiched between a pair of outer race rings of the ball bearing units A and B, it is necessary for the user to have the spacer C coaxially mounted on the rotary shaft D with high accuracy. PA1 a stepped-diameter shaft provided with a large-diameter portion, a small-diameter portion and an annular inner raceway groove directly formed in an outer peripheral surface of the large-diameter portion; PA1 a first outer race ring coaxially disposed around the large-diameter portion of the stepped-diameter shaft and spaced apart therefrom to form an annular space therebetween, the first outer race ring having its inner peripheral surface formed into an outer raceway groove; PA1 a plurality of first balls rotatably mounted in the annular space defined between the annular inner raceway groove of the stepped-diameter shaft and the annular outer raceway groove of the first outer race ring; and PA1 a sleeve-like spacer which is provided with a pair of small-diameter portions in its opposite axial end portions and has one of its small-diameter portions fitted in the first outer race ring and the other fitted in a second outer race of a ball bearing unit which has its inner race ring mounted on the small-diameter portion of the stepped-diameter shaft, the sleeve-like spacer being coaxially disposed around the stepped-diameter shaft while spaced apart therefrom and axially extending between the first outer race and the second outer race of the ball bearing unit which is provided with a plurality of second balls between the inner race ring and the second outer race ring; PA1 an outer diameter of the inner race ring of the ball bearing unit is the same as that of the large-diameter portion of the stepped-diameter shaft; and PA1 an outer and an inner diameter of the second outer race ring of the ball bearing unit are the same as those of the first outer race ring, respectively; PA1 the bearing assembly further comprises a ball retainer coaxially and rotatably mounted in the annular space to rotatably retain the first balls therein. PA1 forming an annular inner raceway groove directly in an outer peripheral surface of a large-diameter portion of a stepped-diameter shaft provided with a small-diameter portion; PA1 mounting a plurality of first balls in an annular space defined between the annular inner raceway groove of the stepped-diameter shaft and an annular outer raceway groove formed in an inner peripheral surface of a first outer race ring which is coaxially disposed around the large-diameter portion of the stepped-diameter shaft so as to be oppositely disposed from the annular inner raceway groove of the stepped-diameter shaft; PA1 coaxially mounting a sleeve-like spacer around the stepped-diameter shaft so as to be spaced apart therefrom, the spacer being provided with a pair of small-diameter portions in its axial end portions and having one of its small-diameter portions coaxially fitted in the first outer race ring; PA1 slidably mounting the other of the small-diameter portions of the spacer in a second outer race ring of a ball bearing unit provided with a plurality of second balls and an inner race ring, the ball bearing unit having its inner race ring slidably mounted on the small-diameter portion of the stepped-diameter shaft; and PA1 bonding the inner race ring of the ball bearing unit to the small-diameter portion of the stepped-diameter shaft by means of an adhesive and like connecting means in a condition in which a predetermined axially inward pre-load is applied to an outer end surface of the inner race ring or the second outer race ring of the ball bearing unit;